Shears or scissors and the like



' "June 21 1927.

- A. T. FIRTH SHEARS 0R SCISSORS AND THE LIKE Filed Jan. 29,

Patented June 21, 1927.

UNITED STATES PATENT OFFICE.

ALFRED r. FIRTH, or New YORK, n. Y.

SHEARS 0R SCISSORS AND THE LIKE.

Application filed January 29, 1926. Serial No. 84,677.

' are connected by an unsubstantial pivot consis-ting of a machine screwthe threaded shank of which is so tightly fitted into one of the membersas to render any adjustment practically impossible.

In both the head and shank of such screw 7 the wearing surface is smalland inadequate to sustain the heavy strain to which the im plement-issubjected. This is particularly the case with large shears, such as areused for cutting metal, and by tailors in cutting heavy cloth. Strain isput upon the narrow wearing surface of the head of the screw by the handof the operator in an. effort to keep the cutting edges of the blades inproper cutting relation.

In ordinary household use or by tailors or clot-h'cutters theapplication of alubricant would result in damage to the'materia-l beingcut, andis therefore impracticable.

A grinding friction therefore takes place on thenarrow marginal surfaceof the pivot head, which results in a loosene'ss and a gradual spreadingapart of the blades which must therefore be forcibly tipped toward theircutting edge to be effective.

This action results in causing the screw head to wear on one side morethan on the other. This causes deterioration of thee-utting edges and ofthe pivot, and renders the use of the implement laborious andannoying.

Other defects and disadvantages are well known and need not be stated.

My improvement consists in the novel feature of construction andarrangement hereina ter particularly decribed and claimed involvingessentially the use of anti-friction balls in connection with novelseating means and pivotal adaptation, whereby the friction is reduced toa minimum, undue wear avoided and the adjustment of the parts, whennecessary rendered easy and within the skill of the ordinary user.

In the accompanying drawings Fig. 1 is a side or face view of a pair ofordinary household scissors or shears embodying my improvements.

Fig. 2 is a section on line XX ofFig. 1.

Fig. 8 isa view, similar to Fig. 1, of a larger size pair of shears.

Fig. 4 is a transverse sectional view of a paid of shear blades on lineYY of Fig.

3, with the pivot and bearing balls omitted. Fig. 5 is a view similar toFig. 3, but with the pivot and balls in place, and'set screw displaced.i Fig. 6 is a central sectional view of the pivot connecting the blades.

The pivot or pintle, which forms an essential part of my invention is inthe form of a bolt, composed of a shank screw-threaded about half itslength, as shown at 2, and provided with a head 3, which is formed witha concave undercut portion 4, which merges 7 into the unthreaded portionof the shank 1; the head 3 is notched across its face as shown at 5, forthe application of a screw-driver to adjust the pivot. The pivot head isof cylindrical fillister form with comparatively deep, peripheral,portion, which allowsit to seat within the correspondingly cylindricaland concentric mouth of the ball holding blade member and rest on theballs belowthc outer surface of the blade.

6 and 7designate the blade'members of the, shears or scissors of which,6 may be termed the upper or right handmember, and 7 the loweror lefthand member, thelatter being formed with a screw threaded hole 8 for thepassage and retention of the thread ed portion of the pivot which ispassed through an opening 9 in the member (Sand firmly screwed to themember 7, so that the member 6 may rotate around the pivot.

The wall of the opening 9 is formed with an annular grooved bearing, 10,and has seated therein the anti-friction'balls 11. The

blade member 6 is formed with an annular pivot head within and embracedby the wall of this socket or bore, the top of the pivot head is broughtclose enough to the blade surface, to avoid unsightly and inconvenientprojection beyond the latter. 7

t the'blade member 7.

screw, the pivot may be adjusted to compen- When the pivot is insertedthrough the member 6, its undercut portion l, contacts withthese balls,and the latter thereby conments of the blades in the act of cuttingarewholly without strain or binding. W hat ever-wear may occur in theconcave portions 4, of the pivot 1, and the groove 10, will becompensated for by the adjustment of the pivot.

In order to retain the pivot at the desired point of adjustment and toprevent any looseness in the connection which might interfere with thee'lliciency of the implement, I provide adequate means for locking thepivot at any position.

For this purpose I form the shank of th pivot with an axiallyscrew-threaded bore or socket 13, to receive a headed setscrew 12.

The external screw threads of the pivot and the threads of the set screw12, run in opposite directions, one being a right hand and the other aleft hand screw, so that any tendency of the pivot to either loosen ortighten, will be opposed by the set-screw, which thus acts as a nutlock.

The proper adjustment of the blades is obtained by screwing the pivotinto the blade 'members 7, so as to bring the two blades as closelytogether as may be desired; and then inserting and tightening up theset-screw 12, until its head impinges against By loosening the setsatefor wear and loosening of the parts! It will be understood that. theshank of the pivot does not extend entirely through the blade member 7,a slight margin of space be- 111;; lelit between its end and the head ofsetscrew to permit the latter to contact with' the surtace ot' the blademember, and avoid being tightened up against theend oi the )ivot headbeing of fillister form, and d Wearing groove former with cylindricasocket extension of appreciable depth, into which the pivot head fitswith its under surface in contact with the balls.

, 2. A cuttingimplement ol the shear type, comprising apair of pivotallyconnected shear members and a connecting pivot, one

ol. said members having an undercut balls contact, sait race in the wallof its pivot hole, with a cylindrical extension forming asocket for thepivot head, and the other a threaded pivot hole in which is adjustablyseated the pivot, and anti-frictionballs seated in said ball race and inbearing contact with the pivot head and shank, belowjthe surface of theshear member, said pivot being cylindrical fillister form, and 7 fittingwith said socket below the blade surface V In testimony whereofI aflixmy signature.

iinrnnn T; FIRTH,

